引导我完成这个例外。我一直在尝试将文件从客户端发送到服务器 - 在客户端手动输入文件的名称。但是我在客户端收到 NullPointerException - 据我所知,可能的错误是“在打开文件之前,我传递了一个空参数,因此是 NPE”
服务器.java
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Server extends Thread {
public static final int PORT = 3333;
public static final int BUFFER_SIZE = 100;
@Override
public void run() {
try {
ServerSocket serverSocket = new ServerSocket(PORT);
while (true) {
Socket s = serverSocket.accept();
saveFile(s);
}
} catch (Exception e) {
e.printStackTrace();
}
}
private void saveFile(Socket socket) throws Exception {
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
FileOutputStream fos = null;
byte [] buffer = new byte[BUFFER_SIZE];
// 1. Read file name.
Object o = ois.readObject();
if (o instanceof String) {
fos = new FileOutputStream(o.toString());
} else {
throwException("Something is wrong");
}
// 2. Read file to the end.
Integer bytesRead = 0;
do {
o = ois.readObject();
if (!(o instanceof Integer)) {
throwException("Something is wrong");
}
bytesRead = (Integer)o;
o = ois.readObject();
if (!(o instanceof byte[])) {
throwException("Something is wrong");
}
buffer = (byte[])o;
// 3. Write data to output file.
fos.write(buffer, 0, bytesRead);
} while (bytesRead == BUFFER_SIZE);
fos.close();
ois.close();
oos.close();
}
public static void throwException(String message) throws Exception {
throw new Exception(message);
}
public static void main(String[] args) {
new Server().start();
}
}
客户端.java
import java.io.File;
import java.io.FileInputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.util.Arrays;
import java.lang.*;
public class Client {
public static void main(String[] args) throws Exception {
String fileName = null;
try {
fileName = args[0];
} catch (Exception e) {
System.out.println("Enter the name of the file :");
}
File file = new File(fileName);
Socket socket = new Socket("localhost", 3333);
ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
oos.writeObject(file.getName());
FileInputStream fis = new FileInputStream(file);
byte [] buffer = new byte[Server.BUFFER_SIZE];
Integer bytesRead = 0;
while ((bytesRead = fis.read(buffer)) > 0) {
oos.writeObject(bytesRead);
oos.writeObject(Arrays.copyOf(buffer, buffer.length));
}
oos.close();
ois.close();
}
}